The Video Electronics Standards Association (VESA) DisplayPort standard defines a flexible system and apparatus capable of transporting video, audio and other data between a Source Device and a Sink Device over a digital communications interface. The Source Device is the master and the Sink Device is the slave. The DisplayPort standard specifies an open digital communications interface for use in both internal connections and external connections regarding display technology. The DisplayPort standard addresses internal connections such as interfaces within a personal computer or monitor. In addition, the DisplayPort standard also addresses external display connections, including interfaces between a personal computer and a monitor or projector, between a personal computer and a television, or between a device such as a digital versatile disk player and a television.
A DisplayPort standard connection consists of three different channels: main link, auxiliary channel and hot plug detect. The main link features one, two or four scalable data pairs (or lanes). The main link transmission rate is determined by a number of factors, including the capabilities of the transmitter and receiver (i.e. Display and Graphics Card) and the quality of the cable. The auxiliary channel is a half-duplex and bi-directional link that is used for command and control functions sent across the interface.
When hot-plugging of the DisplayPort standard connector is detected, via the hot-plug channel, Link Training is initialized. Link Training is a process whereby the correct number of lanes are enabled at the right link rate with the correct drive current and equalization level through a handshake between the DisplayPort transmitter (display) and the receiver (graphics card) via the auxiliary channel (AUX CH). Link Training is successfully completed when the DisplayPort receiver is synchronized to the incoming Main Link data. More specifically, Link Training is considered complete when the bit lock and symbol lock have been achieved on each of the configured lanes and all the lanes are symbol locked with proper inter-lane alignment. After Link Training has been completed the display uses the hot-plug lane to detect changes, such as when a loss of synchronization is detected.
The DisplayPort standard includes both open box-to-box connection, such as when the devices are detachable by an end user and closed, or embedded connections within devices. A closed box-to-box connection between a captive Source Device and a Sink Device pair (which are designed to only work with each other) is regarded as an embedded connection.
For an open, box-to-box connection, the DisplayPort Source Device configures the link through such a Link Training sequence as previously described. However, in the case of a closed or embedded DisplayPort connection, the DisplayPort standard is not ideal. While Full Link Training can establish a link in an embedded connection, it can not ensure that the link is the most optimal for power consumption and signal integrity. In addition, Fast Link training does not allow link status feedback to the Source Device because Hot Plug Detect (HPD) signal can be eliminated in an embedded DisplayPort device interface. Accordingly, for embedded connections, it's common that the system integrator is responsible to ensure the connection meets the requirement of the given application.
A notebook computer is an example of a device incorporating an embedded connection. In today's notebook computers, the notebook panel and the panel interface parameters are fixed and qualified by the notebook design and the Original Design Manufacturer (ODM). Notebook panel interface use pre-calibrated, pre-qualified parameter for the connection which is provided by the notebook design and the ODM.
Accordingly, there is a need for a method and apparatus that will provide improved Link Training for embedded systems employing DisplayPort connectivity. In addition, there is a need for a method and apparatus that will provide for improved power consumption and signal integrity for systems employing DisplayPort connectivity.